Development of a new antimicrobial concept for boar semen preservation based on bacteriocins.

The conventional storage temperature of 16-18 °C provides optimal conditions for the preservation of boar sperm quality, which are extremely cold sensitive cells. On the other hand, however, it requires the addition of antibiotics to inhibit bacterial growth. Rising numbers of antibiotic resistant bacteria call for alternatives to this conventional storing method. As potential alternative, three different bacteriocin candidates with known bacteriolytic activity against E. coli were examined on possible negative effects concerning the sperm quality and on their impact on bacterial growth of E. coli ILSH 02692 in BTS-extended semen w/o antibiotics. Although the lower concentrations (0.01 and 0.25%) of all bacteriocins did not show any impact on the quality of the semen, the higher concentrations (0.5 and 1.0%) of two bacteriocins led to a significant (P < 0.05) reduction in several sperm quality characteristics. The bacteriocin 860/1c after AMS/dialysis did not affect the sperm quality in any of the tested concentrations and in all tested extenders (BTS, MIII, Androstar Premium and Androhep all w/o antibiotics) at 16 °C as well as at 6 °C. This bacteriocin reduced growth of E. coli ILSH 02692 in BTS-extended semen by 50% compared to the control w/o bacteriocin. Furthermore, a preliminary insemination trial indicated no impact of the selected bacteriocin on fertility. These promising results show that the application of bacteriocins in liquid-preserved semen is a feasible possibility in the future.

Comparison of FACSCount AF system, Improved Neubauer hemocytometer, Corning 254 photometer, SpermVision, UltiMate and NucleoCounter SP-100 for determination of sperm concentration of boar semen.

Current research aims at reducing the number of sperm per insemination dose thereby making measurement of sperm concentration in raw semen and the production of uniform insemination doses much more crucial. The present study evaluated the determination of sperm concentration using FACSCount AF System (FACS), Improved Neubauer hemocytometer (HEMO), Corning 254 photometer (Photo C254), SpermVision CASA System (SpermVision), UltiMate CASA System (UltiMate) and NucleoCounter SP-100 (SP-100). The instruments were evaluated with respect to repeatability and to establishing the regression curve towards both HEMO and FACS. Repeatability for the instruments was 2.7, 7.1, 10.4, 8.1, 5.4 and 3.1% for FACS, HEMO, Photo C254, SpermVision, UltiMate and SP-100, respectively. Correlation between instruments was highest between FACS and SP-100. This was made possible due to the high repeatability for both instruments. The agreement between the instruments and HEMO as the gold standard was lower than expected as the largest difference in estimation of concentration was -25 to +50%. The largest percentage difference was observed for measurements of dilute semen. It was clear that percentage difference between instruments depended on sperm concentration. In comparison to the gold standard, agreement was highest between SpermVision and HEMO for dilute semen, but for concentrated semen, agreement was highest between SP-100 and HEMO. However, the agreement between HEMO and all other instruments was not as good as expected. The reason may lie within the presence of agglutinated sperm, preventing proper HEMO counts.